Intake-Manifold Bolt Length Question

patrick · Post by **patrick** » Sat Aug 02, 2008 1:30 pm

I went to the local Kragen and bought some intake manifold bolts made by Spectre Performance that were the correct 3/8-16 size. The applications listed were Chevy, Mopar small and big block, etc. (you get the idea). Although they thread in properly, when I went to seal my intake, a few of the bolts could not get started because they were too short. I noticed they were only one inchers. I can't compare them to the existing ones because the previous owner was like my dad and basically could not find it in him to spend $10 on the correct bolts and as such every bolt was a different grade/length (geez). When I did some research on real Mopar-specific bolts, I notice the length is listed as 1.75 inches, way longer than these one inchers. Is this indeed the correct length? Seems very long, but I just want to use whatever's correct and don't want to destroy any threads on the head. This is for a big block (440, specifically), just in case it differs from a small block. Thanks for all your input. Sorry for the long rambling autistic message.

landon1 · Post by **landon1** » Sat Aug 02, 2008 8:27 pm

i can get back to you when i change out my intake - don't remember too well from when i did my heads, but 1.75 does seem a little long - maybe 1.5??? but, this was like 4 years ago, so i'm not 100% on that

72RoadRunnerGTX · Post by **72RoadRunnerGTX** » Sun Aug 03, 2008 1:00 am

Iâ€™m running 1 3/4â€ grade 5 intake bolts, with washers and brackets taking up some of that length. The threads in the big block heads do pass through into voids in the casting where the push rods pass through the head. Better a tad too long than too short.

patrick · Post by **patrick** » Sun Aug 03, 2008 2:07 am

72RoadRunnerGTX wrote:Iâ€™m running 1 3/4â€ grade 5 intake bolts, with washers and brackets taking up some of that length. The threads in the big block heads do pass through into voids in the casting where the push rods pass through the head. Better a tad too long than too short.

Thanks, looks like 1.75" is correct then. I just didn't want to go too long and ruin anything (remembering 10+ years ago when I used valve-cover screws that were too long and punctured through to the water jackets). Anyway, I went ahead and just bought some off E-bay since they were Mopar specific (and 1.75 inches) and included the bar-end screws and mine are questionable. Geez, did the previous owner have to "Mickey Mouse" EVERYTHING?! Anyway, under $20 is money well spent to me.