Posted By: moparrush
Small Block Heads Question - 01/07/16 07:12 AM
So this my problem. I have rebuilt an 1989 shelby dakota 318 engine. During the rebuild the machinist found that the heads were cracked between the valve seats. These heads are the kidney bean heads which were sort of the cross over between LA heads and the magnum heads. They were only produced for like 3 or 4 years in production trucks and vans. Anyway my machinist tells me that these heads along with the magnum heads have a high rate of cracking between the seats like that. So i go to the salvage yard and find 1990 d150 pull the heads and take them to get done. Again another phone call with bad news that they are cracked too. Mind you that he shows me the cracking when i go back to pick them up. I go through this another couple times swapping the cracked ones for another set from the same years between 88-91. Same darn cracks. Si i found a set off a 1985 360 that looked to be in excellent shape and pulled those. Now these are not the kidney bean heads but i figured that they didnt seem any different. So i had them re worked and installed them on the engine.
Another point to let you know is that these engines are roller lifters motors. Well i got the motor installed got the truck fired up and it runs good except that the valve train sounds like a broken sewing machine running. Alot of excessive noise. A good mopar buddy and engine builder thouhht maybe it was a pushrod issue, so he had a bunch of different length pushrods from .025 over stock length to .175 over stock length and ive tried them all. The engine wont even fire with anything but the stock length in place.
So obviously its not a pushrod issue. The lifters are brand new, no broken springs (thier new too) or anything else i can readily see.
So i have a 3.9 in another dakota i have and pulled the valve covers off. The 3.9 is a 318 minus 2 cylinders. Uses the same pushrod lengths etc etc. It appears to me that the hole/guide in the head which the push rod passes thru on its way from the rocker arm to the lifter is much larger on my 3.9 vice the 1985 360 heads that i have installed. I chunked the original heads to a scrap bin some months ago so i cant compare the original heads to these earlier LA heads.
So my question is does anyone know if you can use an LA head on these pre magnum dodge roller small blocks?
I think the sound i hear coming from the valve train is that the pushrods are hitting during the travel up and down on those guide holes in the head. Yes both sides are doing it to. Yes i have the rockers in the correct right hand lrft hand locations and yes i have the intake and exhaust rockers in thier correct location too. As you may know the exhaust rocker has amachined out recess for valve spring clearance.
So has anybody had this problem and if so what is the solution? Am i screwed and have to try and find a good set of those pre magnum kidney bean heads?
Thanks everyone for any help you can offer!
Another point to let you know is that these engines are roller lifters motors. Well i got the motor installed got the truck fired up and it runs good except that the valve train sounds like a broken sewing machine running. Alot of excessive noise. A good mopar buddy and engine builder thouhht maybe it was a pushrod issue, so he had a bunch of different length pushrods from .025 over stock length to .175 over stock length and ive tried them all. The engine wont even fire with anything but the stock length in place.
So obviously its not a pushrod issue. The lifters are brand new, no broken springs (thier new too) or anything else i can readily see.
So i have a 3.9 in another dakota i have and pulled the valve covers off. The 3.9 is a 318 minus 2 cylinders. Uses the same pushrod lengths etc etc. It appears to me that the hole/guide in the head which the push rod passes thru on its way from the rocker arm to the lifter is much larger on my 3.9 vice the 1985 360 heads that i have installed. I chunked the original heads to a scrap bin some months ago so i cant compare the original heads to these earlier LA heads.
So my question is does anyone know if you can use an LA head on these pre magnum dodge roller small blocks?
I think the sound i hear coming from the valve train is that the pushrods are hitting during the travel up and down on those guide holes in the head. Yes both sides are doing it to. Yes i have the rockers in the correct right hand lrft hand locations and yes i have the intake and exhaust rockers in thier correct location too. As you may know the exhaust rocker has amachined out recess for valve spring clearance.
So has anybody had this problem and if so what is the solution? Am i screwed and have to try and find a good set of those pre magnum kidney bean heads?
Thanks everyone for any help you can offer!